1. Technical Field
Several aspects of the present invention relate to a manufacturing method of an electrode assembly, an electrode assembly and a battery.
2. Related Art
A lithium battery using lithium or lithium-containing material as a negative electrode is lightweight and has a high capacity, and further, a high voltage can be obtained by combination with a suitable positive electrode. Thus, the lithium battery is widely used as a battery for a portable electric equipment, a camera, a watch, an electric tool, a hybrid vehicle and the like. However, in the lithium battery, since lithium has high activity and an organic electrolytic solution is used, fire and explosion can occur at short-circuit. Accordingly, in the design of the lithium battery, securement of safety is an important problem.
One of methods of enhancing the safety is not to use an electrolytic solution (ceasing of use of electrolytic solution). As one of attempts to cease the use of electrolytic solution, a lithium polymer battery using a gel polymer electrolyte is developed. However, since the gel polymer electrolyte is such that an organic electrolyte is impregnated in the polymer gel, there is yet a problem of fire and explosion.
As another attempt to cease the use of electrolytic solution, a lithium battery using a ceramic electrolyte (inorganic solid electrolyte) is developed (see, for example, JP-A-2006-277997 (Patent Literature 1), JP-A-2004-179158 (Patent Literature 2), Japanese Patent No. 4615339 (Patent Literature 3)). When the ceramic electrolyte is used, since ions moving in the electrolyte by a battery reaction become only lithium ions, a side reaction hardly occurs. Besides, since a combustible organic solution is not used, a seal member and a liquid sealing structure are not required, and more reduction in size and thickness becomes possible.
In the technique disclosed in Patent Literature 1, there is a problem that contact at an interface between a ceramic electrolyte powder and an electrode active material or an interface between a ceramic electrolyte powder and a ceramic electrolyte powder becomes insufficient, and an excellent battery output can not be obtained. Further, there is a problem that the interface contact becomes unstable by volume change due to a charge-discharge cycle, and the cycle life is deteriorated.
In the technique disclosed in Patent Literature 2, there is a problem that manufacture of a battery having sufficient capacity is difficult. In order to obtain sufficient capacity for the battery, manufacture of an active material having a total thickness of more than 100 μm is required. However, according to the technique of Patent Literature 2, the manufacture of the active material having a thickness of more than 100 μm is difficult.
In the technique disclosed in Patent Literature 3, there is a problem that Li0.35La0.55TiO2 as a solid electrolyte and LiCoO2 as a battery active material diffuse in solid phase in a manufacture process, and electric characteristics are deteriorated.